[RESEND][PATCH v5 2/3] spi: spi-ti-qspi: add mmap mode read support

ti-qspi controller provides mmap port to read data from SPI flashes. mmap port is enabled in QSPI_SPI_SWITCH_REG. ctrl module register may also need to be accessed for some SoCs. The QSPI_SPI_SETUP_REGx needs to be populated with flash specific information like read opcode, read mode(quad, dual,

[RESEND][PATCH v5 2/3] spi: spi-ti-qspi: add mmap mode read support

ti-qspi controller provides mmap port to read data from SPI flashes. mmap port is enabled in QSPI_SPI_SWITCH_REG. ctrl module register may also need to be accessed for some SoCs. The QSPI_SPI_SETUP_REGx needs to be populated with flash specific information like read opcode, read mode(quad, dual,